Sandwich panel, insert therefor, structure comprising sandwich panels and method of joining such panels

ABSTRACT

A sandwich panel including a core material sandwiched between plate members, and an insert member locally replacing the core and having a profile so as to intermesh with an appropriately profiled member on the unit to which it to be connected as well as a method of connecting sandwich panels by inserting an insert member having a profiled side so as to interlock with an appropriately profiled member on the unit to which it is to be connected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods of joining sandwich panels and tosandwich panels themselves having means to connect to other sandwichpanels or structural or non structural units.

2. Discussion of Prior Art

Sandwich panels comprise a core material (such as honeycomb) sandwichedbetween plates of stiff material. These composite panels haveapplication in a wide variety of areas due to significant mass savingsand their high strength/stiffness to weight ratio and thus their use inlightweight structures. Thus they have application in the construction,aerospace and other fields.

It is a requirement that these panels be joined so as to form astructure and in such a way that they are able to withstand and transmitloads.

Alternative methods of joining sandwich panels have been developed. FIG.1a shows a simple way of joining two panels at 90°. This is done byextending one of the plates of one of the panels and using adhesive toconnect to the cut end of the other. This joint is however extremelyweak in many modes.

Alternatively cleats are known which produce fairly strong jointingbetween panels. These cleats consist of shaped plates which are used ina variety of modes. FIGS. 1b and 1 d show two panels joined at 90° and a“T” joint respectively. The panels of FIGS. 1b and d are joined in eachcase by two L-shaped cleats 7. The interfaces between the panels and thejoining surface of the cleats are provided with adhesive. Alternativelythe cleats may be mechanically fastened or a combination of both. In analternative mode the cleats are shaped to provide a slot for insertionof the panels as shown at 8 in FIG. 1c. This has the advantage inproviding a stronger connection. However the use of cleats is notwithout problems. Firstly there is the problem that cleats areadditional components which add to the cost as well as the increase intime in joining and assembling sandwich panels. Cleats having slots forinsertion of the panels have to be accurately sized which isproblematic. Heat or cold will often complicate accurate fitting asthere is frequently thermal mismatch. In addition the use of cleats doesnot provide smooth joining. These may reduce aerodynamic performance inparticular applications as well as making it more difficult to installunits internally.

An alternative method of joining sandwich panels is disclosed inDE-A-2166396. The sandwich panels are provided with recesses formed fromshell connectors which are embedded within the panel at the edge of ajoint between shell halves. A latching profile is provided which mayeither plug the recess to provide structural support at the joint andprotect the recess or provide connection between two or more panelshaving appropriately contoured recesses.

It is an object of the invention to provide a method of joining sandwichpanels which is simple, effective and provides a good joint wherebyforces are transmitted across members efficiently.

SUMMARY OF THE INVENTION

The invention comprises a sandwich panel comprising a core materialsandwiched between plate members, and an insert member locally replacingthe core and having a profiled side so as to intermesh with anappropriately profiled member on a second sandwich panel to which it isto be connected.

The insert is preferably corrugated. It is preferably fabricated from ahigh strength lightweight material such as carbon fibre reinforcedplastic.

The advantages are that the corrugated sections interlock on assemblyproviding additional surface areas for adhesive in shear. No matching ofhoney comb or other filler material is required. The joining gives alightweight structure with give good compression strength, excellentdistribution of forces (especially shear). The appropriate use of apotting compound is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereinafter be described by way of example only andwith reference to the following figures of which:

FIGS. 1(a)-1(d) show various prior art methods of joining two panels.

FIG. 2 shows an embodiment of the corrugated joint in accordance withthe present invention.

FIGS. 3(a) and 3(b) show various profiles of insert members.

FIGS. 4(a) and 4(b) show 45° and 135° angle joints using the corrugateddesign.

FIG. 5 shows a further embodiment of the invention whereby the insert isused in a “T” joint.

DETAILED DISCUSSION OF PREFERRED EMBODIMENTS

FIG. 2 shows two honeycomb panels 1 and 2 each having a honeycomb centre3 sandwiched between two face skin plates 4. One of the skin plates ofeach panel is extended such that it is greater in length than itsopposite plate. The honeycomb core does not extend to the edge of theshort plate but terminates a short distance from it. A corrugated member9 is inserted between the two plates of each panel such that they extendfrom the honeycomb material to be flush with the longer plate. Inassembly the two panels are effectively joined by pushing the panelstogether such that the corrugated inserts mate to produce a snug fit.Adhesive is preferably applied.

FIG. 3 shows a corrugated section bonded into a honey comb sandwichpanel.

The skilled person would understand that the inserts can be of anysuitable shape. The corrugations may be of a wide variety of shapes,such as square or rectangular. Moreover the inserts do not need to becorrugated.

FIGS. 3(a) and 3(b) show various end profiles of inserts. FIGS. 3a, b,show a corrugated insert and a solid rectangular cut-out insert. As faras these profiles are concerned they are preferably uneven such that thedistance β and α are substantially the same thus allowing a good fit ofidentical inserts with each other. This leads perforce to the distance δbeing less than β and α and thus to “uneven” inserts. The mainconsideration is that they have a profile which can mate with a profileon another insert to produce a snug fit. Preferably the inserts extendbetween the faceskins down to the core material (honeycomb).

Preferably the inserts are corrugated as this allows for a lightweightinsert with large stiffness.

To improve further the integrity of the join, adhesive is preferablyused.

FIGS. 4(a) and 4(b) show two honey comb panels comprising plates andhoney-comb filler, joined at 45° and 135°. Each panel angle jointcomprises inserts suitably angled and profiled. The cross-hatched “area”shows the bond area which is in shear.

FIG. 5 shows a further embodiment of the invention whereby the insert isused in a “T” joint. Two sandwich panels are shown 1,2. A corrugatedinsert 9 is bonded between two faceskins 3 a, b of the panel 2 with theinner face skin 3 a removed at the location of the joint. The adjoiningpanel has an insert which has lugs 11 that correspond to the pitch ofthe corrugated section. These may be manufactured from a compositeblock, which is inserted between the skin plates of the panel. In thisembodiment although the outer skin has been cut the forces within theskin can be transferred by the adhesive in shear through the corrugatedsection.

What is claimed is:
 1. A structure comprising: a sandwich panelcomprising a core material sandwiched between plate members and aprofiled member located between the plate members at a selectedposition; and a unit joined to said sandwich panel comprising a secondprofiled member intermeshing with said profiled member of said sandwichpanel; said intermeshing profiled members defining a plurality of pairsof closely confronting surfaces perpendicular to the planes of saidplate members between which surfaces adhesive is applied to bond saidprofiled members together and whereby loads tending to separate saidpanel and unit, in a direction opposite to the relative movement bywhich said profiled members are intermeshed, can be transferred betweensaid profiled members through said adhesive in shear.
 2. A structureaccording to claim 1 wherein said unit is a second sandwich panelcomprising a core material sandwiched between plate members and saidsecond profiled member is located between the respective plate membersat a selected position.
 3. A structure according to claim 2, wherein, inat least one of said sandwich panels, one of the plate members is longerthan the other and the respective profiled member extends so as to besubstantially flush with the edge of said longer plate member.
 4. Astructure according to claim 1, wherein the profile of each saidprofiled member is corrugated.
 5. A structure comprising, a firstsandwich panel; and a second sandwich panel; each of said panelscomprising a core material sandwiched between plate members and aninsert member between the respective plate members, each of said insertmembers presenting a profile in the form of rectangular corrugationshaving successive crowns and troughs, the widths of said crowns and thewidths of said troughs substantially equal, and said panelsinterconnected by intermeshing of said profiles.
 6. A structureaccording to claim 5, wherein said profiles are bonded together byadhesive.
 7. A structure comprising: a first sandwich panel; a secondsandwich panel; each of said panels comprising a core materialsandwiched between plate members and an insert member between therespective plate members, said insert members having respective profilesinterengaged to positionally locate said panels relative to each other,each said profile in the form of rectangular corrugations havingsuccessive crowns and troughs, the widths of said crowns and the widthsof said troughs substantially equal; and adhesive for adhesively bondingthe insert members to each other.
 8. A structure comprising: a sandwichpanel comprising a core material sandwiched between plate members and aprofiled member located between the plate members at a selectedposition; and a unit jointed to said sandwich panel comprising a secondprofiled member intermeshing with said profiled member of said sandwichpanel, the profile of each said profiled member is in the form ofrectangular corrugations having successive crowns and troughs, thewidths of said crowns and the widths of said troughs substantiallyequal; said intermeshing profiled members defining a plurality ofconfronting surfaces perpendicular to the planes of said plate membersbetween which surfaces adhesive is applied to bond said profiled memberstogether and whereby loads in a direction tending to separate said paneland unit can be transferred between said profiled members through saidadhesive in shear.
 9. A method of joining a sandwich panel to anotherunit, the sandwich panel comprising a core material sandwiched betweenplate members and a first profiled member located between the platemembers of said sandwich panel at a selected position; said unitcomprising a second profiled member complementary to the first profiledmember, said profiled members shaped to define a plurality of pairs ofclosely confronting surfaces perpendicular to the planes of said platemembers when said profiled members are intermeshed; and the methodcomprising: intermeshing said profiled members by relative movementbetween them and with adhesive applied between said confronting surfaceswhereby to bond said profiled members together and whereby loads tendingto separate said panel and unit, in a direction opposite to saidrelative movement can be transferred between said profiled membersthrough said adhesive in shear.
 10. A method according to claim 9wherein said other unit is a second sandwich panel comprising a corematerial sandwiched between plate members and said second profiledmember is located between the respective plate members at a selectedposition.